JPH0631245A - Anticorrosive coating method for steel material - Google Patents

Abstract

PURPOSE:To provide a coating having excellent anticorrosive performance and high adhesiveness for steel material wherein a paint film of primer is not deteriorated by a method wherein specific heat-resistant, anticorrosive coating material, as primer, is applied to the surface of steel material and after the primer is dried, specific powder coating material is applied thereto and baked. CONSTITUTION:Anticorrosive coating method for steel material is such that heat- resistant, anticorrosive coating material having anode activity, wherein zinc dust is contained and hydrolytic initial condensation product of alkyl silicate or a mixture of initial condensation product and colloidal silica, as vehicle resin component, is used as a principal component, is applied to the surface of steel material as primer and after the primer is dried, powder coating material having thermal shrinkage stress of 40kg/cm<2> or less is applied thereto and baked. The heat-resistant, anticorrosive coating material is not influenced by the baking temperature during baking and it produces a highly anticorrosive effect as a primer having anode activity due to zinc dust and further the powder coating material has low thermal shrinkage stress and when the paint film shrinks after being applied and baked, the paint film of the heat- resistant, anticorrosive coating material is prevented from being separated from the surface of the steel material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an anticorrosion coating method for steel materials used when constructing large steel structures such as ships, plants and bridges.

[0002]

2. Description of the Related Art Steel plates, which are used in ships, plants, bridges, etc., are covered with mill scale (rust), so they are removed by physical means such as shot blasting or chemical means. After that, a zinc-based shop primer is applied as a primary rust preventive paint with a dry film thickness of about 5 to 30 μ,
Processing such as fusing and welding is performed with a rust preventive coating so that rust does not occur again on the surface. After such processing is performed, solvent-type paint is further applied on the shop primer in a dry film thickness of about 100 to 500 μm.

Since the shop primer is applied to a flat steel material, it can be applied automatically by a coating facility in a factory, and there is no particular problem even if it is a solvent type. However, since the paint to be applied on top of it is manually applied in a timely manner according to the process, it is necessary to pay attention to a worker's health hazard due to the solvent in the paint and a risk of fire if it is a solvent type. There is also the problem of air pollution, which is the volatilization of the solvent into the atmosphere. Especially in recent years, from the viewpoint of environmental protection and occupational safety and health, the movement toward solvent-free paints has become predominant.
Powder coatings such as epoxy resin-based powder coatings are regaining attention as solvent-free coatings that do not contain solvents. In particular, the epoxy resin-based powder coating material has high durability and is therefore a powerful powder coating material for ships.

On the other hand, the zinc-based shop primer has a corrosion resistance even in a thin film due to the anode effect of the zinc dust contained therein, so that a primary corrosion protection capable of fusion welding of steel materials for large steel structures such as ships, plants and bridges. It is indispensable as a paint. Therefore, in the case of using powder paint, after coating the shop primer on the surface of the steel material and performing processing such as fusing welding, the powder paint is applied and baked on the surface to perform the coating. .

[0005]

However, in order to form a coating film by baking, melting and curing the powder coating material, heat shrinkage stress occurs when the coating film of the powder coating material is left to cool, Due to the heat shrinkage stress of the powder coating film, there is a problem that a force in a direction that causes the coating film of the shop primer from the surface of the steel material acts to reduce the adhesion of the coating film to the steel material. Further, there is a problem that the coating film of the shop primer is deteriorated by the action of a high temperature of about 150 to 250 ° C. when baking the powder coating material, and in this respect also, the adhesion of the coating film to the steel material may be deteriorated. .

The present invention has been made in view of the above points, and a powder coating is used as a coating material for overcoating, the primer coating film does not deteriorate, and the corrosion resistance is excellent, and the adhesion to a steel material is improved. The purpose is to make it possible to perform high-level painting.

[0007]

Coating of steel according to the present invention
The method includes zinc dust and uses an alkyl resin as a vehicle resin component.
Rusilate hydrolysis initial condensate or the initial condensation
Based on a mixture of metal and colloidal silica
Using a heat-resistant anticorrosive paint with activity as a primer for steel
After coating the surface and drying the above primer, heat shrinkage stress
40 kg / cm ²Paint and bake the following powder paint
It is characterized by that.

The present invention will be described in detail below. In the present invention, a heat-resistant anticorrosive paint having an anode activity is used as a shop primer, and zinc powder is blended as an anode active pigment. Zinc dust is blended so as to be at least 30% by weight of the dry coating film. If the content of zinc dust is less than 30% by weight, sufficient corrosion resistance cannot be imparted to the primer. The vehicle resin component of this primer is mainly composed of an alkyl silicate hydrolyzed initial condensate or a mixture of the initial condensate and colloidal silica in order to have heat resistance.

Among these, the vehicle resin component has a general formula of Si (R ₁ ) _x (OR ₂ ) _4-x (wherein R ₁ is an alkyl group or an alkenyl group having up to 5 carbon atoms, and R ₂ is 5 carbon atoms). Up to alkyl group, x is 0 or 1
It means that the initial condensate obtained by hydrolyzing at least one kind of alkoxysilane of (1) and solvent-type colloidal silica are contained. Hydrolysis of the alkoxysilanes can be carried out by using a suitable aqueous acid solution such as dilute hydrochloric acid in a lower alkanol such as isopropyl alcohol. The mixing ratio of the hydrolyzed initial condensate of the alkoxysilane and the solvent-type colloidal silica is 10/90 to 85/15 in terms of SiO ₂ fraction.
Is preferred. The SiO ₂ fraction of the hydrolyzed initial condensate of alkoxysilane and solvent-type colloidal silica is 10/9.
If it is less than 0, the film-forming state of the coating film tends to be poor, and conversely if it exceeds 85/15, the heat resistance of the coating film tends to be poor.

A paste obtained by using this vehicle resin component as a coating liquid component, and dispersing zinc dust, a coloring pigment, an extender pigment, a rust preventive pigment, and other additives in an alcohol-based or ether-based solvent. Is used as a heat-resistant anticorrosion paint, and the paint liquid component and the paint paste component are mixed and sufficiently stirred just before the painting.

Further, in the present invention, as the powder coating material, one having a heat shrinkage stress of 40 kg / cm ² or less at the time of baking and curing is used. Heat shrinkage stress is 40 kg / cm ²
By using the following powder coating, as described below,
It is possible to prevent the adhesion failure due to the coating of the heat resistant anticorrosion coating which is the base coating of the powder coating, and more preferably the heat shrinkage stress is 30 kg /
It is preferable to use an epoxy resin type having a cm ² or less and high impermeability to corrosive substances.

As the epoxy resin powder coating material having a low heat shrinkage stress of 40 kg / cm ² or less, polysulfide modified epoxy resin, primary hydroxyl group-containing glycol modified epoxy resin, dimer acid modified epoxy resin, CT
BN (Carboxyl reactivityterminal position Butadie
ne Acrylonitrile) modified epoxy resin, ATBN (Amine
reactivity terminal position Butadiene Acrylonitr
ile) at least one kind of flexible epoxy resin such as modified epoxy resin and silyl group-containing epoxy resin, or modification obtained by addition reaction of these flexible epoxy resins with glycidyl ether type epoxy resins of bisphenol A and bisphenol F An epoxy resin or a mixture of these flexible epoxy resin or modified epoxy resin and a glycidyl ether type epoxy resin of bisphenol A or bisphenol F is used as a vehicle resin component, and a component known as a curing component of an epoxy resin powder coating, that is, Curing components such as phenolic resins, amide-based resins, amine-based resins, polyester-based resins, hydrazide-based resins, acid anhydrides, and coloring pigments, extender pigments, rust-preventive pigments, etc. Pigment, leveling effect, pinhole prevention effect, dispersion Effect coating 10 wt% or less of the acrylic resin as the component capable of imparting, urea resins, those prepared by blending an additive such as a silicone resin can be exemplified.

Then, the vehicle resin component, the curing component, the pigment and the additive are put in a mixing hopper, preliminarily kneaded with a high speed mixer or the like, and then heat kneaded with a heating kneader or the like. The heated and kneaded product is allowed to cool to a sheet-like shape to solidify it, and the solidified product is roughly pulverized and finely pulverized to adjust the particle size suitable for coating such as electrostatic coating, and finally the classification treatment. A powder coating material can be prepared by carrying out the method.

Here, the heat shrinkage stress in the present invention means
Baking powder coating at 150-250 ℃ (melting / curing)
After the cooling, the heat shrinkage stress value is the stress generated by the shrinking action of the coating film when it is allowed to cool.
It can be calculated according to the following formula provided by Yukihiko Inoue, "Study of Fiber-Induced Body Paint (5th-6th Report)", pp. 148, pp. 43, 1994 (reference material: Kozo Sato, "Outline""Physical Engineering of Paint", Science and Engineering Publishing Company, published in 1973).

That is, the powder coating material is applied to a thin plate such as phosphor bronze having a known Young's modulus, baked in a drying furnace under the baking conditions of the powder coating material, and then left to cool in a constant temperature bath at 20 ° C. and 65% RH. . At this time, since the shrinkage of the coating film is larger than that of a thin plate such as phosphor bronze as a base material, the coated plate is curved. Then, one hour after baking and allowing to cool, the metal sheet 1 coated as shown in FIG. 1 is set on the knife edge 2,
The length and deflection can be read with a microscope, and the value of heat shrinkage stress can be calculated by the following formula.

[0016]

[Equation 1]

P: heat shrinkage stress (kg / cm ² ) h ₁ ; thickness of coating h ₂ ; thickness of thin metal plate ν ₁ ; Poisson's ratio of coating ν ₂ ; Poisson's ratio of thin metal E ₁ ; coating Young's modulus of film E ₂ ; Young's modulus of thin metal plate ρ; radius of curvature (ρ = l ² / 8δ + δ / 2) l; distance between knife edges δ; flexure width For the above heat-resistant anticorrosive paint and powder paint It is possible to compound any additive used in general paints such as leveling agents, thixotropic agents, antifoaming agents, etc. within the range not departing from the present invention, and also compounded in heat resistant anticorrosive paints and powder paints. Use clay, talc, precipitated barium sulfate, etc. as extender pigments, iron oxide, titanium oxide, cyanine blue, etc. as color pigments, and zinc phosphate, zinc chromate, strontium chromate, etc. as anticorrosion pigments. Can be made of aluminum Um powder, mica powder, glass flakes and the like powdery substance or flakes, may be blended fibrous material or the like.

After removing the mill scale on the surface of steel materials such as steel plates and steel pipes by physical means or chemical means, first, the heat resistant anticorrosive paint is applied on the surface of steel materials as a shop primer. The coating can be performed by a commonly used method such as an airless automatic coating machine so that the dry film thickness becomes 5 to 30 μm.
Drying and curing of this heat resistant anticorrosion paint can be performed by leaving it to stand naturally, but if urgent coating of powder paint is required due to process reasons, etc., it can be exposed to warm steam or sprayed with acid / base containing water. You may make it harden | cure.

As described above, the heat-resistant anticorrosive paint is applied as a shop primer on the surface of the steel material and subjected to rust-prevention treatment, and then the processing such as fusing and welding is performed. After performing such processing, the powder coating material is applied on the primer coating film. The powder coating can be applied by using an electrostatic coating machine or the like, and the coating amount is preferably set so that the dry film thickness is 70 to 500 μm. A coating film of powder coating can be formed by baking and drying (melting / curing) after applying the powder coating, but baking is performed in a gas furnace, electric furnace, far infrared furnace, high frequency heating furnace, etc. It can be performed using a furnace.
The baking temperature and baking time differ depending on the type of resin used in the powder coating, the heat source system of the drying furnace, etc., but generally 1
It is preferable to bake at a temperature of 50 to 250 ° C., and the time is appropriately set in consideration of furnace conditions, steel material thickness and the like.

As described above, the steel material can be subjected to anticorrosion coating by coating the surface of the steel material with the heat resistant anticorrosive coating material and the powder coating material. In this product, the heat-resistant anticorrosive paint has excellent heat resistance, so it is not affected by the baking temperature at the time of baking the powder paint, and has a high anticorrosive effect as a primer having anodic activity due to zinc powder. In addition, the heat-resistant anticorrosive paint is used as a primer (undercoating film), and the powder paint applied on it has a heat shrinkage stress of 40 kg / cm ^2.
Since it is as low as the following, when the coating film of the powder coating material shrinks after applying and baking the powder coating material, the coating film of the powder coating material causes the coating film of the heat resistant anticorrosive coating material to be caused from the surface of the steel material. The force applied is small, and there is no fear that the adhesion of the coating film of the heat-resistant anticorrosion paint on the surface of the steel material will be reduced, and sufficient adhesion can be maintained. Therefore, in the present invention, it is possible to obtain a coated surface of a steel material having excellent corrosion resistance and salt water resistance and water resistance, and the present invention is a ship, a river or a sea that sails on a coast where a corrosive environment is severe. It is possible to provide an optimal coating method for a plant, a ship's hold, etc., which is exposed to a material having high coating permeability such as a bridge, crude oil and the like.

[0021]

EXAMPLES Next, the present invention will be described in detail by examples. (Production Example A of heat resistant anticorrosive coating) Tetraethoxysilane 100 Vinyl trimethoxysilane 20 Isopropyl alcohol 122.3 0.01N Hydrochloric acid 21 (263.3 parts by weight in total) Into a reaction container, hydrochloric acid was added dropwise over 1 hour while stirring at 40 ° C., and stirring was continued for 1 hour after completion of the addition to obtain an alkoxysilane hydrolysis initial condensate.

Next, a heat-resistant anticorrosive paint A comprising the initial condensate and colloidal silica was prepared by blending the initial condensate in the following blending amounts. The ignition loss of the binder component of the heat resistant anticorrosive coating material A was 24% by weight.・ Initial condensate 25 ・ Solvent type colloidal silica (15% by weight) 25 ・ Zinc dust 35 ・ Burning clay 14.5 ・ Dag inhibitor 0.5 (total 100 parts by weight) Solvent type colloidal silica is methanol silica sol (Nissan (Manufactured by Kagaku) was diluted with isopropyl alcohol to adjust the SiO ₂ content to 15% by weight.

(Production Example B of Heat-Resistant Anticorrosion Paint) -Tetraethoxysilane 100-Isobutyl Alcohol 50-Isopropyl Alcohol 24.7-Water 16.6-0.1N Hydrochloric Acid 0.7 (Total 192 parts by weight) In the above formulation Add the remaining components excluding hydrochloric acid and water to the reaction vessel, keep the mixture at 40 ° C and stir to mix hydrochloric acid and water.
After dropwise addition over a period of time, stirring was continued for 1 hour after completion of the dropwise addition to obtain an alkoxysilane hydrolysis initial condensate.

Next, a heat-resistant anticorrosive paint B comprising the initial condensate and colloidal silica was prepared by blending the initial condensate in the following amounts. The ignition loss of the binder component of this heat-resistant anticorrosion coating material B was 24% by weight. -Initial condensate 40-Solvent type colloidal silica (15% by weight) 10-Zinc dust 30-Burning clay 24.5-Anti-sagging agent 0.5 (total 105 parts by weight) (Production Example C of epoxy resin powder coating)・ Epomic SR35 * 1 61.0 ・ Epicure 171 * 2 14.8 ・ Titanium oxide 11.8 ・ Clay 11.9 ・ Leveling agent 0.5 (total 100 parts by weight) The above composition was pre-kneaded with a high speed mixer, Furthermore, heat and knead with a Busco kneader and let cool with a belt cooler.
After coarsely pulverizing, finely pulverizing with an atomizer, and further passing through each step of classification with a sea bar, epoxy resin powder coating C
Was prepared.

(Production Example D of epoxy resin powder coating material) -Epicoat DX355 * 3 62.7-N-12 * 4 13.1-Titanium oxide 11.8-Clay 11.9-Leveling agent 0.5 (total) 100 parts by weight) An epoxy resin powder coating material D was prepared in the same manner as in Production Example C with the above formulation.

(Production Example E of Epoxy Resin Powder Coating) -Epicoat DX355 * 3 63.1-Epicure 171 * 2 12.7-Titanium oxide 11.8-Clay 11.9-Leveling agent 0.5 (total 100) Parts by weight) An epoxy resin powder coating material E was prepared in the same manner as in Production Example C with the above composition.

(Production Example F of epoxy resin powder coating material) -Epicoat 1004 * 5 57.1-Epicure 171 * 2 14.5-Titanium oxide 11.2-Clay 16.7-Leveling agent 0.5 (total 100) By weight) An epoxy resin powder coating material F was prepared in the same manner as in Production Example C with the above formulation.

In the production example of the epoxy resin powder coating material, * 1 to * 5 are as follows. * 1 "Epomic SR35"; Mitsui Petrochemical Co., Ltd., rubber modified epoxy resin, epoxy equivalent 1000 * 2 "Epicure 171"; Yuka Shell Epoxy Co., Ltd., phenolic resin curing agent, active hydrogen equivalent 250 * 3 "Epicoat DX355"; manufactured by Yuka Shell Epoxy Co., Ltd., dimer acid-modified epoxy resin, epoxy equivalent 1200 * 4 "N-12"; manufactured by Nippon Hydrazide Industry Co., Ltd., dodecanoic acid dihydrazide, active hydrogen equivalent 130 * 5 "Epicoat 1004""Yukaka Shell Epoxy Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent 950, epoxy resin powder coatings C to F prepared as described above.
The heat shrinkage stress was measured by the method described above. The results are shown in Table 1. As shown in Table 1, the epoxy resin powder coatings C, D and E each have a heat shrinkage stress of 40 kg / c.
Since it is as small as m ² or less and can be used as a powder coating material specified in the present invention, the epoxy resin powder coating material F has a heat shrinkage stress of more than 40 kg / cm ² , so it should be used as a powder coating material specified in the present invention. I can't.

[0029]

[Table 1]

(Example 1) The heat-resistant anticorrosive paint A obtained in Production Example A was applied to a shot-blasted steel plate (steel plate: SS-41, surface treatment: JIS G 3101, size: 3.2 mm x 7).
5 mm × 150 mm) was coated as a shop primer with an airless coating machine so that the dry film thickness would be 15 μm. After leaving it to stand for 10 days in the open air, the epoxy resin powder coating material C obtained in Production Example C was applied to a dry film thickness of 300 μ using an electrostatic coating machine, and the coating was carried out in a hot-air electric furnace.
The plate was left standing at 00 ° C. for 25 minutes for baking and drying, and the steel sheet was anticorrosion coated.

(Examples 2 to 6) As shown in Table 2, heat-resistant anticorrosive coatings A and B and epoxy resin powder coatings C, D and E were used in combination, and the dry coating film thicknesses shown in Table 2 were used. The steel plate was anticorrosion coated in the same manner as in Example 1 so that

[0032]

[Table 2]

(Comparative Examples 1 to 4) As shown in Table 3, a shop primer and an epoxy resin powder coating material were used in combination, and the dry coating film thickness shown in Table 3 was obtained in the same manner as in Example 1. The steel plate was anti-corrosion coated. In Comparative Examples 2 and 3, a commercially available epoxy-based zinc primer (“Nippe Zinky 8000” manufactured by Nippon Paint Co., Ltd .; zinc-rich paint containing an epoxy resin as a vehicle component) was used as a shop primer. In Comparative Example 4, the epoxy resin powder coating material C was directly coated on the surface of the shot-blasted steel plate without using the shop primer.

[0034]

[Table 3]

The following tests were conducted on the coated steel sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 4 above. (Test 1; initial adhesion) Baking of powder coating (200 ° C
(× 25 minutes) After drying, let it cool at room temperature for 1 hour, and
5400 8.5. 1 ”In accordance with the cross-cut adhesion test evaluation method, 25 cuts are made by making 6 vertical and horizontal cuts in the coating film with a cutter knife at intervals of 2 mm until reaching the steel plate surface An adhesion test with a tape was performed. Measure the number of squares of the coating film peeled off from the steel plate and
IS K 5400 8.5.1 (5) "
An evaluation score of 0 to 0 was given.

At the same time, the adhesion of the coating film was measured by using an adhesion tester manufactured by Elcometer. (Test 2; Adhesion after immersion in salt water) In order to investigate the durability of the coating film in salt water, the coated steel sheet was immersed in a 3% NaCl aqueous solution in a constant temperature water bath constantly kept at 40 ° C, and after 3 months. Take out the coated steel sheet from the immersion liquid, perform a cross-cut adhesion test as in Test 1, and evaluate the degree of rust on the coating surface by AS.
It carried out according to TM D610-68.

(Test 3; Adhesion after Salt Spray Test) In order to investigate the durability of the coating film in salt spray, the coated steel sheet was set under the conditions specified in "JIS K 5400 9.1". It was subjected to a spray test apparatus for 700 hours. 700
After a lapse of time, a cross-cut adhesion test is performed in the same manner as in Test 1, and the degree of rust generation on the coating surface is evaluated by ASTM D610.
It carried out according to -68.

The results of each of the above tests are shown in Tables 4 and 5.

[0039]

[Table 4]

[0040]

[Table 5]

As can be seen from Table 4, in each of the examples, the initial adhesion, the adhesion after immersion in salt water, and the adhesion after the salt spray test were evaluated in a cross-cut adhesion of 8 points or more. Adhesion test evaluation value is 20kg / cm ²
From the above, it is confirmed that the coating film adhesion is good. It is also confirmed that the coated steel sheet has no rust after the immersion in salt water and after the salt spray test, and that the steel sheet has good rust preventive properties. As described above, since each of the examples has good adhesion resistance in a salt water environment and good rust preventive property, it is evaluated as an optimum anticorrosive material coating system for steel structures such as ships. You can do it.

On the other hand, as shown in Table 5, in Comparative Example 1 using the epoxy resin powder coating material having a large heat shrinkage stress of 62 kg / cm ² , the initial adhesion was 2 points in the cross-cut adhesion evaluation. Adhesion test 5kg
It was as low as / cm ² or less and could not be put to practical use. Further, in Comparative Examples 2 and 3 in which a non-heat-resistant epoxy zinc primer was used as the shop primer, the primer coating film deteriorated due to the influence of the temperature during baking of the powder coating material, and the coating system was not durable. Met. Furthermore, in Comparative Example 4 in which the powder coating was directly applied to the surface of the steel sheet without using the shop primer, the coated steel sheet was rusted in the rust occurrence test and the rust prevention was poor, and the adhesion and durability were also poor. It was inferior.

[0043]

As described above, the present invention contains zinc dust,
Alkyl silicate hydrolysis initial condensate as a vehicle resin component, or a heat-resistant anticorrosive paint having an anodic activity mainly composed of a mixture of the initial condensate and colloidal silica is applied on the surface of a steel material as a primer, and after the primer is dried, Since the powder paint with a heat shrinkage stress of 40 kg / cm ² or less is applied and baked, the heat-resistant anticorrosive paint has excellent heat resistance and is not affected by the baking temperature when baking the powder paint. As a primer having an anode activity due to zinc dust, it can obtain a high anticorrosion effect, and the powder paint has a low heat shrinkage stress, and the coating film of the powder paint shrinks after applying and baking the powder paint. When applied, the force of the powder coating to act to cause the coating of the heat resistant anticorrosive coating from the steel surface is small. A than are those that can maintain sufficient adhesion without reducing the adhesion of the coating film of heat-based anticorrosive paint to the surface of the steel material.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a method of measuring heat shrinkage stress.

[Explanation of symbols]

 1 sheet metal 2 knife edge

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[Procedure amendment]

[Submission date] August 9, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

A method for coating a steel material according to the present invention includes a zinc powder and a general formula as a vehicle resin component.
Is Si (R ₁ ) _x (OR ₂ ) _4-x (wherein R ₁ is an alkyl group having up to 5 carbon atoms or an alkenyl group).
Group, R ₂ is an alkyl group having up to 5 carbon atoms, x is 0 or 1
Means at least one alkoxysilane (wherein
(Including partial condensates of alkoxysilane)
The obtained initial condensate or a heat-resistant anticorrosive paint having an anodic activity mainly composed of a mixture of the initial condensate and colloidal silica is applied as a primer on the surface of a steel material, and after the primer is dried, the heat shrinkage stress is 40 kg. /
It is characterized in that a powder paint having a size of cm ² or less is applied and baked.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

The present invention will be described in detail below. In the present invention, a heat-resistant anticorrosive paint having an anode activity is used as a shop primer, and zinc powder is blended as an anode active pigment. Zinc dust is blended so as to be at least 30% by weight of the dry coating film. If the content of zinc dust is less than 30% by weight, sufficient corrosion resistance cannot be imparted to the primer. The vehicle resin component of the primer in order to include a heat-resistant, A
The main component is a hydrolytic precondensate of rucoxysilane or a mixture of the precondensate and colloidal silica.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction content]

[0043]

As described above, the present invention contains zinc dust,
The vehicle resin component has a general formula of Si (R ₁ ) _x (OR ₂ ) _4-x (wherein R ₁ is an alkyl group having up to 5 carbon atoms or an alkenyl group).
Group, R ₂ is an alkyl group having up to 5 carbon atoms, x is 0 or 1
At least one alkoxysilane)
An initial condensate obtained by water decomposition or a heat-resistant anticorrosive paint having an anodic activity mainly composed of a mixture of the initial condensate and colloidal silica is applied on the surface of a steel material as a primer, and after the primer is dried, heat is applied. Shrinkage stress is 4
Since the powder paint of 0 kg / cm ² or less is applied and baked, the heat-resistant anticorrosive paint has excellent heat resistance and is not affected by the baking temperature when baking the powder paint. As a primer with activity, it is possible to obtain a high anticorrosion effect, and the powder coating has low heat shrinkage stress, and when the coating film of the powder coating shrinks after coating and baking the powder coating, The force that acts to cause the coating of the heat resistant anticorrosion coating from the surface of the steel material by the coating of the body paint is small,
Sufficient adhesion can be maintained without lowering the adhesion of the coating film of the heat resistant anticorrosive paint on the surface of the steel material.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Akihiro Ueda 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (72) Inventor Shinichi Ishihara 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Within the corporation

Claims (4)

[Claims] 1. A heat-resistant anticorrosive paint having an anode activity, which contains zinc dust and contains an alkyl silicate hydrolyzed initial condensate as a vehicle resin component or a mixture of the initial condensate and colloidal silica as a main component, is used as a primer for a steel material. A method for anticorrosive coating of steel material, which comprises coating the surface, drying the primer, and then coating and baking a powder coating material having a heat shrinkage stress of 40 kg / cm ² or less. 2. A heat-resistant anticorrosive paint containing zinc powder as an anode active pigment in an amount of at least 30% by weight of a dry coating film, and having a general formula of Si (R ₁ ) _x (OR ₂ ) _4-x (formula) as a vehicle resin component. Wherein R ₁ is an alkyl group or an alkenyl group having up to 5 carbon atoms, R ₂ is an alkyl group having up to 5 carbon atoms, and x is 0 or 1
Which means that the initial condensate obtained by hydrolyzing at least one alkoxysilane and solvent-type colloidal silica are contained at a ratio of SiO _{2 of} 10/90 to 85/15. Item 1. A method for anticorrosion coating of steel according to Item 1. 3. The anticorrosion coating method for a steel material according to claim 1, wherein the powder coating material is an epoxy resin powder coating material. 4. The anticorrosion coating method for a steel material according to claim 1, wherein the coating amounts of the primer and the powder coating material are 5 to 30 μ and 70 to 500 μ, respectively, in terms of dry film thickness. .